Experimental and Theoretical Studies on the Shear Performance of Concrete Beams Reinforced with Fiber-Reinforced Polymer Stirrups.

In this paper, the shear behavior of concrete beams reinforced with FRP stirrups is studied. The shear performances of six concrete beams with a size of 150 mm × 300 mm × 3000 mm under four-point loading up to failure were experimentally analyzed. The critical parameters included the shear span to depth ratio (λ) and stirrup spacing (S). The test results revealed that as λ increased from 1 to 2, 3, and 4, the ultimate shear capacity of the beam decreases by 50.5%, 67.7%, and 69.2%, respectively. Meanwhile, as S increased from 100 mm to 150 mm and 200 mm, the ultimate shear capacity decreased by 16.1% and 44.6%, respectively. A new shear capacity calculation model of concrete beam reinforced with FRP stirrups was also proposed, which further considered the shear capacity of the FRP stirrups on the basis of the shear capacity of an RC beam without stirrups using the strut-and-tie model. Finally, the experiment and calculation results of 56 beam specimens reinforced with FRP stirrups extracted from this paper and previous studies were compared using the calculation models proposed in this paper, in order to evaluate the accuracy of these calculation models.

Cloning, expression analysis and localization of DAZL gene implicated in germ cell development of male Hezuo pig.

Deleted in azoospermia-like (DAZL) is essential for mammalian testicular function and spermatogenesis. To explore the molecular characterization, expression patterns, and cellular localization of the DAZL in Hezuo pig testes, testicular tissue was isolated from Hezuo pig at five development stages including 30 days old (30 d), 90 days old (90 d), 120 days old (120 d), 180 days old (180 d), and 240 days old (240 d). DAZL cDNA was first cloned using the RT-PCR method, and its molecular characterization was analyzed using relevant bioinformatics software. Subsequently, the expression patterns and cellular localization of DAZL were evaluated using quantitative real-time PCR (qRT-PCR), Western blot, and immunohistochemistry. The cloning and sequence analysis showed that the Hezuo pig DAZL cDNA fragment contained 888 bp open reading frame (ORF) capable of encoding 295 amino acid residues and exhibited high identities with some other mammals. The qRT-PCR and Western blot results indicated that DAZL was specifically expressed in Hezuo pig testes, and DAZL levels of both mRNA and protein were expressed at all five reproductive stages of Hezuo pig testes, with extremely significant higher expression levels in 90 d, 120 d, 180 d, and 240 d than those in 30 d (p < 0.01). Additionally, immunohistochemistry results revealed that DAZL protein was mainly localized in gonocytes at 30 d testes, primary spermatocytes, and spermatozoon at other developmental stages, and Leydig cells throughout five development stages. Together, these results suggested that DAZL may play an important role by regulating the proliferation or differentiation of gonocytes, development of primary spermatocytes and spermatozoon, and functional maintenance of Leydig cells in testicular development and spermatogenesis of Hezuo pig. Nevertheless, the specific regulatory mechanisms underlying these phenomena still requires further investigated and verified.

Overexpression of SIRT1 alleviates oxidative damage and barrier dysfunction in CPB2 toxin-infected IPEC-J2 cells.

Clostridium perfringens (C. perfringens) beta2 (CPB2) toxin may induce necrotizing enteritis (NE) in pigs. Sirtuin1 (SIRT1) is involved in inflammatory intestinal diseases and affects intestinal barrier function. However, the effects of SIRT1 on piglet intestinal disease caused by CPB2 toxin are unclear. This study revealed the role of pig SIRT1 in CPB2 toxin-exposed intestinal porcine epithelial cells (IPEC-J2). Herein, we manifested that SIRT1 was dramatically decreased in IPEC-J2 cells infected with CPB2 toxin. Subsequently, we silenced and overexpressed SIRT1 using siRNA and a overexpression vector in CPB2 toxin-treated IPEC-J2 cells. The results indicated that overexpression of SIRT1 suppressed reactive oxygen species (ROS) generates, the expression tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and Bax, nuclear factor-kappa B (NF-κB p65), phospho (p)-NF-kB p65 and lactate dehydrogenase (LDH) activity and apoptosis in CPB2 toxin-treated IPEC-J2 cells, and increased IL-10, mitochondrial membrane potential (ΔΨm), Bcl-2, Claudin1 and Occludin levels and cell viability. These results indicated that SIRT1 protects IPEC-J2 cells against CPB2 toxin-induced oxidative damage and tight junction (TJ) disruption, which provides a theoretical basis for further study of the molecular regulatory mechanism of SIRT1 in C. perfringens-infected NE in piglets.

Cloning of STC-1 and analysis of its differential expression in Hezuo pig.

The purpose of this study was to examine STC-1's structure, function, and differential expression in large and miniature pigs. We cloned the Hezuo pig's coding sequence, compared its homology, and used bioinformatics to assess the structure. RT-qPCR and Western blot were used to detect the expression in ten tissues of Hezuo pig and Landrace pig. The results showed that Hezuo pig was most closely related to Capra hircus and most distantly related to Danio rerio. The protein STC-1 has a signal peptide and its secondary structure is dominated by the alpha helix. The mRNA expression in the spleen, duodenum, jejunum, and stomach of Hezuo pigs was higher than that of Landrace pigs. And except for heart and duodenum, expression of the protein in Hezuo pig was higher than in another. In conclusion, STC-1 is highly conserved among different breeds of pigs, and the expression and distribution of its mRNA and protein are different in large and miniature pigs. This work can lay the foundation for future study into the mechanism of action of STC-1 in Hezuo pigs and the enhancement of breeding in miniature pigs.

In Silico Exploration and Biological Evaluation of Bispecific Peptides Derived from Anti-HER2 Antibodies and Peptide-Camptothecin Conjugates for HER2-Positive Breast Cancer.

To enhance the affinity of the human epidermal growth receptor 2 (HER2) targeted peptide developed previously, bispecific fusion peptides P1GCGT1 and P1GCGCGT1 were designed using an in silico approach. Molecular dynamic simulation showed that both peptides strongly interacted with HER2 domains II and IV. Compared with peptides targeting each single domain, P1GCGT1 and P1GCGCGT1 could bind to HER2 more significantly and targeted HER2-positive cells specifically. Additionally, both peptides were used to generate peptide-drug conjugates with camptothecin (CPT), among which I-1 and I-4 were screened for enhanced cellular activity and selectivity. Biological evaluation demonstrated that I-1 and I-4 induced cell apoptosis, promoted cell cycle arrestin S-phase, and inhibited Topo I activity. The binding affinity assay and confocal analysis revealed that I-1 and I-4 were effective at targeting HER2. Moreover, I-1 and I-4 showed better stability than single targeting peptide and presented enhanced antitumor activity and safety than CPT in tumor-bearing mice.

Integrated analysis of miRNA and mRNA expression profiles in testes of Landrace and Hezuo boars.

Precocious puberty is closely related to testicular development and spermatogenesis, and there is increasing evidence that miRNAs are involved in regulation of testicular development and spermatogenesis. However, little is known about the regulation of microRNAs (miRNAs) during precocious maturation in Hezuo (HZ) boars. In this study, serum Testosterone (T), Estradiol (E2), Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) levels were detected in HZ and Landrace (LC) boars in the postnatal period at 30, 90, 120, 180, and 240 days, and the testes of HZ and LC boars at 30 and 120 days were used for histological observation. In addition, we performed small RNA-Seq to identify miRNA at sexual immaturity (30-days-old) and maturity (120-days-old) of HZ boar testis (using LC boar as control) to reveal the key miRNA in regulation of precocious puberty. Hormone assay results showed that high levels of T, E2, FSH, and LH may be related to precocious sexual maturity of HZ boars, and that FSH may play an important function before sexual maturity. Histological observation showed that HZ boars developed earlier than LC boars and had reached sexual maturity at 120 days. Small RNA-Seq yielded a total of 359 exist miRNAs, 767 known miRNAs and 322 novel miRNAs in 12 samples; 549, 468, 133, and 247 differentially expressed (DE) miRNAs were identified between Ha vs. Hb, La vs. Lb, Ha vs. La, and Hb vs. Lb (log2 fold change >1 and p < 0.05). Enrichment analysis showed that target genes of these DE miRNAs were enriched in many gene ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathways (such as PI3K-Akt, Hippo and Rap1 signaling pathways) were related to testicular development and spermatogenesis. Further screening, some miRNAs (such as ssc-miR-29b, ssc-miR-199b, ssc-miR-383, ssc-miR-149, ssc-miR-615, and ssc-miR-370) were possibly associated with precocious puberty. These results provide new light on miRNA regulatory mechanisms involved in precocious puberty.

Experimental and Theoretical Study on Flexural Behavior of GFRP- and CFRP-Reinforced Concrete Beams after High-Temperature Exposure.

In this study, in order to study the flexural behavior of fiber-reinforced polymer (FRP) bars with reinforced concrete beams under static loads after high-temperature exposure, seven pieces of FRP-reinforced concrete beams were subjected to static bending tests and calculation model derivations. Four-point bending tests were carried out on FRP-reinforced concrete beams after high temperature treatment. The effects of high temperature and types of FRP bars on the cracking load, crack development, deflection and ultimate capacity, and failure mode of concrete beams were investigated. The test results show that the maximum crack width, deflection, and ultimate bearing capacity of GFRP- and CFRP-reinforced concrete beams decrease obviously with a rise in high temperature. After the exposure of 400 °C for 2 h, compared with the behavior of concrete beams at room temperature, the maximum crack width of GFRP and CFRP-reinforced concrete beams increased by 42.9% and 41.7%, respectively, the deflection increases by 103.6% and 22.0%, and the ultimate bearing capacity decrease by 11.9% and 3.9%. Meanwhile, through the analysis of the existing research results and test results, the calculation models for the maximum crack width, deflection, and residual ultimate capacity of FRP-reinforced concrete beams after exposure of high temperature were proposed. For FRP-reinforced concrete beams after high-temperature exposure, the errors between the measured maximum crack width, stiffness, residual bearing capacity, and their corresponding calculated values using the model were mostly less than 10%. The calculated value using the proposed model in this research is in good agreement with the measured value. The mechanical properties of FRP-reinforced high-strength concrete structures after high-temperature exposure can be preliminarily predicted, which provides a new theoretical basis for the application of FRP-reinforced concrete structures.

Eco-Friendly, High-Ductility Slag/Fly-Ash-Based Engineered Cementitious Composite (ECC) Reinforced with PE Fibers.

Engineered cementitious composites (ECCs) are a special class of ultra-ductile fiber-reinforced cementitious composites containing a significant amount of short discontinuous fibers. The distinctive tensile strain-hardening behavior of ECCs is the result of a systematic design based on the micromechanics of the fiber, matrix, and fiber-matrix interface. However, ECCs require extensive cement content, which is inconsistent with the goal of sustainable and green building materials. Consequently, the objective of this study is to investigate the mechanical performance of slag/fly-ash-based engineered cementitious composites (ECCs) reinforced with polyethylene (PE) fiber under axial compressive loading, as well as direct tensile and flexural strength tests. The composites' microstructure and mineralogical composition were analyzed using images obtained from scanning electron microscopy (SEM), X-ray energy diffraction spectroscopy (EDS), X-ray powder diffraction (XRD), and X-ray fluorescence (XRF). The experimental results reveal that a slag-containing composite mixture shows strain-hardening behavior and comparable ductility properties to those of fly-ash-based composite mixtures. A ternary system of binder materials with 5% and 15% slag can increase the compressive strength of ECC by 3.5% and 34.9%, respectively, compared to slag-free ECC composite. Moreover, the microstructural results show that the slag-based cementitious matrix has a more closely cross-linked and dense microstructure at the matrix-aggregate interface. In addition, the concentration of particles on the surface of the fibers was higher in the slag-based cementitious composites than in the fly ash-based composite. This supports the concept that there is a stronger bonding between the fibers and matrix in the slag-based cementitious matrix than in fly-ash-based matrix.

Effect of Elevated Temperature on Mechanical Properties of High-Volume Fly Ash-Based Geopolymer Concrete, Mortar and Paste Cured at Room Temperature.

This paper presents results from experimental work on mechanical properties of geopolymer concrete, mortar and paste prepared using fly ash and blended slag. Compressive strength, splitting tensile strength and flexural strength tests were conducted on large sets of geopolymer and ordinary concrete, mortar and paste after exposure to elevated temperatures. From Thermogravimetric analyzer (TGA), X-ray diffraction (XRD), Scanning electron microscope (SEM) test results, the geopolymer exhibits excellent resistance to elevated temperature. Compressive strengths of C30, C40 and C50 geopolymer concrete, mortar and paste show incremental improvement then followed by a gradual reduction, and finally reach a relatively consistent value with an increase in exposure temperature. The higher slag content in the geopolymer reduces residual strength and the lower exposure temperature corresponding to peak residual strength. Resistance to elevated temperature of C40 geopolymer concrete, mortar and paste is better than that of ordinary concrete, mortar and paste at the same grade. XRD, TGA and SEM analysis suggests that the heat resistance of C-S-H produced using slag is lower than that of sulphoaluminate gel (quartz and mullite, etc.) produced using fly ash. This facilitates degradation of C30, C40 and C50 geopolymer after exposure to elevated temperatures.

Experimental Study on Bond Performance of Carbon- and Glass-Fiber Reinforced Polymer (CFRP/GFRP) Bars and Steel Strands to Concrete.

FRP bars and steel strands are widely used in civil engineering. In this study, three different types of high-strength reinforcement materials, carbon fiber reinforced polymer (CFRP) bar, glass fiber reinforced polymer (GFRP) bar, and steel strand, were investigated for their interfacial bond performance with concrete. A total of 90 sets of specimens were conducted to analyze the effects of various parameters such as the diameter of reinforcement, bond length, the grade of concrete and stirrup on the bond strength and residual bond strength. The results show that CFRP bars possess a higher bond strength retention rate than steel bars in the residual section. In addition, with the increase in bond length and diameter of the CFRP bar, the residual bond strength decreases, and the bond strength retention rate decreases. Furthermore, the bond strength retention rate of GFRP bars was found to be higher than that of CFRP bars. With the increase in grade of concrete, the bond strength and residual bond strength between GFRP bars and concrete increases, but the bond strength retention rate decreases. With an increase in bond length and diameter of the GFRP bar, the bond strength starts to decrease. Further, stirrup can also increase the bond strength and reduce the slip at the free end of GFRP bars. Moreover, the bond strength retention rate of the steel strand was found to be lower than CFRP and GFRP bar.

Fatigue Behavior of Glass Fiber-Reinforced Polymer Bars after Elevated Temperatures Exposure.

Fiber-reinforced polymer (FRP) bars have been widely applied in civil engineering. This paper presents the results of an experimental study to investigate the tensile fatigue mechanical properties of glass fiber-reinforced polymer (GFRP) bars after elevated temperatures exposure. For this purpose, a total of 105 GFRP bars were conducted for testing. The specimens were exposed to heating regimes of 100, 150, 200, 250, 300 and 350 °C for a period of 0, 1 or 2 h. The GFRP bars were tested with different times of cyclic load after elevated temperatures exposure. The results show that the tensile strength and elastic modulus of GFRP bars decrease with the increase of elevated temperature and holding time, and the tensile strength of GFRP bars decreases obviously by 19.5% when the temperature reaches 250 °C. Within the test temperature range, the tensile strength of GFRP bars decreases at most by 28.0%. The cyclic load accelerates the degradation of GFRP bars after elevated temperature exposure. The coupling of elevated temperature and holding time enhance the degradation effect of cyclic load on GFRP bars. The tensile strength of GFRP bars after elevated temperatures exposure at 350 °C under cyclic load is reduced by 50.5% compared with that at room temperature and by 36.3% compared with that after exposing at 350 °C without cyclic load. In addition, the elastic modulus of GFRP bars after elevated temperatures exposure at 350 °C under cyclic load is reduced by 17.6% compared with that at room temperature and by 6.0% compared with that after exposing at 350 °C without cyclic load.